Loading unit for telephone systems.



G A. KELSALL LOADING UNIT FOR TELEPHONE SYSTEMS. I APPLICATION FILED DEC-29.15MB.

/nvenf0r: (ho/70 ,9. Ke/sa/A Patented Aug. 28, 1917.

UNITED STATES PATENT @FFTQE.

GEORGE A. KELSALL, OF NEW YORK, N. Y., ASSIGNOR To WEsTERN ELECTRIC CCMPANY, INCORPORATED, 012 NEW YORK, N. Y., A CORPORATION CE NEW YORK.

LOADING UNIT FOR TELEPHONE SYSTEMS.

Application filed December 29, 1916.

T all whom it may concern:

Be it known that I, GEORGE A. KELsALL, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Loading Units for Telephone Systems. of which the following is a full, clear, concise, and exact description.

This invention relates to loading units for telephone systems, and particularly to a loading unit adapted for the simultaneous loading of two physical circuits and their derived or phantom circuits.

In an arrangement described and claimed in an application of J. B. Speed, Serial No. 88,072, filed March 31, 1916, and assigned to the same assignee as the present application, the simultaneous loading of two phys ical circuits and their derived phantom circuit is provided for by means of a loading unit Characterized by two toroidal core members intersecting on a common diameter. In said loading unit, the two line windings individual to one of the physical circuits are located on opposite halves of one toroid, and the line windings individual to the other physical circuit are located on opposite halves of the other toroid. Each physical circuit is thus loaded independently of, and without interference with, the other physical circuit. Furthermore, when phantom circuit currents flow through the windings of this loading unit, the distribution of flux is such as to load the phantom circuit in addition to the physical circuits.

It is an inherent characteristic of a load ing unit of the kind just described that the mutual inductances between all line wind ings are very nearly equal, as a result of which th phantom circuit inductance is only fifty per cent. of the physical circuit inductance. This is due to the fact that for phantom circuit operation the two line windings of each toroid are connected in parallel and the two parallel circuits thus formed are connected in series. The resultant inductance therefore is equal to that operative in a single line winding; that is, the selfinductance of a line winding plus its mutual inductance to an adjacent winding. The mutual effects of the remaining windings being in opposite directions cancel each other. The physical circuit inductance on the other hand is that due to two line windings in series, which in effect is the sum of Specification of Letters Patent.

Patented Aug. 28, 1917.

Serial No. 139,531.

the two self-inductances plus twice their mutual inductance. It has been found in practice, however, taking into consideration the mutual capacity of the phantom circuit as compared with the mutual capacity of the physical circuit, that, in order to load a phantom circuit to the best advantage, its inductance should be approximately sixty per cent. ofthe physical circuit inductance.

The present invention may be considered an improvement upon the invention covered by the application of J. B. Speed hereinbefore mentioned, in that it modifies the relation of the physical circuit inductance to the phantom circuit inductance so that the latter is approximately sixty per cent. of the former, thereby satisfying the requirement before mentioned.

The invention is characterized by the provision in the magnetic structure of gaps of high reluctance which are so located that they increase the reluctance of the paths traversed by the physical circuit flux, but do not substantially increase the reluctance of the paths traversed by the phantom circuit flux; thus destroying the balance between the mutual inductances previously re ferred to so as to add the phantom circuit inductance and at the same time subtract from the physical circuit inductance.

The invention will be understood from the following description taken in connection with the accompanying drawing, in which Figure l is a perspective view of a loading unit embodying one form of the invention; and Figs. 2 and 3 are perspective Views of core members for loading units embodying other forms of the invention.

The core members shown in Figs. 1, 2 and 3 and hereafter described may be of any suitable magnetic material. For example, they may conveniently be formed of finely divided iron, the individual particles of which are insulated from one another, the core material being molded by high pressure, in the manner described and claimed in an application for patent of J. B. Speed, Serial No. 89,409, filed April 6, 1916, and assigned to the same assignee as the present application. Such core material may be readily worked to the desired shapes by molding and cutting.

Referring to Figs. 1, 2 and 8, the core structure of each loading unit is shown as comprising two toroidal core members 1 and 2 arranged to intersect at right angles on a common diameter. Ways in which the core members 1 and 2 engage will be clear from the drawing. In Fig. 1, windings 3 and -l are shown located upon opposite halves of core member 1, and are intended for inclusion in the line conductors of one physical circuit; and windings 5 and 6 are located upon the opposite halves of core member 2, and are adapted for inclusion in the line conductors of the other physical circuit, as described in the aforesaid application of J. B. Speed, Serial No. 88,072. The whole structure may be held together in any suitable manner, as by a belt of tape 7 encircling the structure and held taut by cords 55, substantially as shown in Fig. 1. The core structures shown in Figs. 2 and 3 may be similarly provided with windings, and may be held together in the same manner.

Figs. 1, 2 and 3 show diiferently shaped gaps of high reluctance which may be located in the core members 1 and 2 at their points of juncture. All of said gaps extend radially through the points of juncture of the core members 1 and 2, but do not completely intersect said core members. As shown in Fig. 1, the gaps are in the form of slots 11 and 12 located, respectively, in the core members 1 and 2 at their points of juncture, and in planes at substantially right angles to one another. As shown in Fig. 2, the gaps are in the form of round holes 13 and 11 through the core members 1 and 2 at their points of juncture. And in the core structure shown in Fig. 3, the gaps are in the form of crossed slots in the core members 1 and 2 at their points of juncture. Said gaps may be either left unfilled or may be filled with some non-magnetic material, such as fiber, for purpose of mechanical strength, as shown at 15 in Fig. 8.

As explained in the aforesaid application of J. B. Speed, Serial No. 88,072, the physical circuitfiux due to the windings 3 and 4;, threads and is confined to the core member 1; and the physical circuit flux due to the windings 5 and 6, threads and is confined to the core member 2; and the phantom circuit flux due to said windings all passes from one point of juncture through the two halves of core member 1 to the other juncture, and back through the two halves of the other core member 2 to the first-mentioned juncture. In Figs. 1, 2 and 8, the paths of the physical circuit flux are indicated by arrows made with full lines; and the paths of the phantom circuit flux are indicated by arrows made with dash lines.

It will be obvious from the foregoing description and from the drawin that the gaps of high reluctance of the various forms shown and described, will increase the reluctance in paths traversed by the physical circuit flux without substantially increasing the reluctance of the paths traversed by the phantom circuit flux. By suitably proportioning said gaps, it is possible to make the reluctance of the path traversed by the phantom circuit flux such that the inductance operative in the phantom circuit is substantially sixty per cent. of that operative in each of the physical circuits; which is the relation desired, as hereinbefore explained.

It will be understood that, while in the drawing core structures are shown in which the core members are substantially square in cross-section, they may, if desired, have other cross-sectional. forms. The term toroid used herein is intended to refer to a ring of any desired cross section. It will also be understood that, instead of rings, rectangular or other forms of frames and closed figures might be employed, and that, for want of some broader expression, the term toroid is used to denote all such structures.

What is claimed is:

1. A loading unit having a plurality of core members each in the form of a closed figure, said members intersecting at a plurality of points and being provided with gaps of high reluctance at the intersections.

2. In a loading unit for physical and phantom circuits, intersecting core members having gaps at the intersections, said gaps offering different reluctances to physical and phantom circuit flux.

3. A loading unit having two toroidal core members intersecting on a common diameter and having gaps of high reluctance therein at the points of juncture of said members.

4:. A loading unit having two toroidal core members intersecting on a common diameter and having gaps of high reluctance therein extending radially through the points of juncture of said members.

A loading unit having two toroidal core members intersecting on a common diameter and having gaps of high reluctance therein in the form of openings extending radially through but not completely intersecting said members at their points of juncture.

6. A loading unit having two toroidal core members intersecting on a common di ameter and having gaps of high reluctance therein in the form of slots passing radially through said members at their points of juncture, said slots being in planes at substantially right angles to one another.

In witness whereof, I hereunto subscribe my name this 28th day f December, A. D.

GEORGE A. KELSALL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

